Thermodynamic Evaluation on Alkoxyamines of TEMPO Derivatives, Stable Alkoxyamines or Potential Radical Donors?

Qian, Bao‐Chen; Zhang, Lu; Zhang, Gao‐Shuai; Fu, Yan‐Hua; Zhu, Xiao‐Qing; Shen, Guang‐Bin

doi:10.1002/slct.202204144

Cited by 4 publications

(3 citation statements)

References 111 publications

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“…However, the more activated tris(trimethylsilyl)silane reacts efficiently with TEMPO through intermolecular HAT, and tetramethylpiperidine, derived from trapping of the silyl radical with TEMPO and subsequent cleavage of the N−O bond, was detected as the major product. 222,1090 The reaction of Si−H bonds with TEMPO to give TEMPO−Si adducts was also documented for Si (100) and Si (111) surfaces. 1091 In a recent report by the groups of Chen and Fan, the silylation of alcohols was described by using silanes and a catalytic amount of 4-NH 2 -TEMPO under argon atmosphere.…”

Section: Oxidation Of Silanes Stannanes and Germanesmentioning

confidence: 86%

“…The less reactive trialkyl silanes do not engage in a HAT to TEMPO. However, the more activated tris(trimethylsilyl)silane reacts efficiently with TEMPO through intermolecular HAT, and tetramethylpiperidine, derived from trapping of the silyl radical with TEMPO and subsequent cleavage of the N–O bond, was detected as the major product. , …”

Section: Oxidation Reactionsmentioning

confidence: 99%

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Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

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Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R 1 R 2 N−O • . The spin distribution over the nitroxide N and O atoms contributes to the thermodynamic stability of these radicals. The presence of bulky N-substituents R 1 and R 2 prevents nitroxide radical dimerization, ensuring their kinetic stability. Despite their reactivity toward various transient C radicals, some nitroxides can be easily stored under air at room temperature. Furthermore, nitroxides can be oxidized to oxoammonium salts (R 1 R 2 N�O + ) or reduced to anions (R 1 R 2 N−O − ), enabling them to act as valuable oxidants or reductants depending on their oxidation state. Therefore, they exhibit interesting reactivity across all three oxidation states. Due to these fascinating properties, nitroxides find extensive applications in diverse fields such as biochemistry, medicinal chemistry, materials science, and organic synthesis. This review focuses on the versatile applications of nitroxides in organic synthesis. For their use in other important fields, we will refer to several review articles. The introductory part provides a brief overview of the history of nitroxide chemistry. Subsequently, the key methods for preparing nitroxides are discussed, followed by an examination of their structural diversity and physical properties. The main portion of this review is dedicated to oxidation reactions, wherein parent nitroxides or their corresponding oxoammonium salts serve as active species. It will be demonstrated that various functional groups (such as alcohols, amines, enolates, and alkanes among others) can be efficiently oxidized. These oxidations can be carried out using nitroxides as catalysts in combination with various stoichiometric terminal oxidants. By reducing nitroxides to their corresponding anions, they become effective reducing reagents with intriguing applications in organic synthesis. Nitroxides possess the ability to selectively react with transient radicals, making them useful for terminating radical cascade reactions by forming alkoxyamines. Depending on their structure, alkoxyamines exhibit weak C−O bonds, allowing for the thermal generation of C radicals through reversible C−O bond cleavage. Such thermally generated C radicals can participate in various radical transformations, as discussed toward the end of this review. Furthermore, the application of this strategy in natural product synthesis will be presented.

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Section: Oxidation Of Silanes Stannanes and Germanesmentioning

confidence: 86%

Section: Oxidation Reactionsmentioning

confidence: 99%

Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

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“…1–4 In recent years, the selectivity and reactivity of these nitrogen-containing heterocycles as hydrogen atom donors (H-donor), XH, in hydrogen atom transfer reactions (HAT, X–H + Y → X + Y–H) have attracted significant attention from a large number of researchers, gradually becoming a research hotspot. 5–12 Accordingly, it is necessary to develop methods to evaluate the H-donating ability of these nitrogen-containing heterocyclic compounds as H-donors using their characteristic physical parameters. Also, it is important to quantitatively study the H-donating abilities and compare the antioxidant activities of antioxidants.…”

Section: Introductionmentioning

confidence: 99%

Quantitative evaluation of H-donating abilities of C(sp³)–H bonds of nitrogen-containing heterocycles in hydrogen atom transfer reaction

Jia

Shen

et al. 2023

RSC Adv.

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α‐Hydrogen spirocyclic alkoxyamines synthesis: ESR verified Nitroxides generation and their potential application in NMP polymerization

Guerrero‐Caicedo,

Pardo‐Tamayo,

Romero

et al. 2023

ChemistrySelect

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Herein, we report a synthetic methodology towards the construction of new cylic alkoxyamines without the prior obtention of their respective nitroxides. These systems are constituted by an indene core connected to a pyrrolidine nucleus through a spiro carbon atom, containing an adjacent α‐hydrogen to the N atom, in order to exhibit the 1‐azaspiro[4.4]nonane frame. Alkoxyamines were synthesised by a free radical‐based spirocyclization, starting from functionalized oxime ethers, involving aryl and neutral alkoxyaminyl radicals in 16–40 % yields. Then, the novel spirocyclic aminoxyl radicals (nitroxides) were detected in ESR spectra, when alkoxyamines were subjected by the thermal homolytic cleavage of their −C−O−N− bond. In general, the temperatures found were in accordance with the increase in the stability of the carbon‐centred radical for the same type of nitroxides. In addition, a spirocyclic alkoxyamine 8 b with α‐hydrogen was employed as initiators/mediators in the styrene bulk homopolymerization, obtaining high conversions and relatively narrow dispersity (Ð~1.5). This suggests that the synthetic methodology used in this research work to obtain α‐hydrogen spirocyclic alkoxyamines would have the potential to be applied in nitroxide‐mediated polymerization (NMP).

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Thermodynamic Evaluation on Alkoxyamines of TEMPO Derivatives, Stable Alkoxyamines or Potential Radical Donors?

Cited by 4 publications

References 111 publications

Organic Synthesis Using Nitroxides

Organic Synthesis Using Nitroxides

Quantitative evaluation of H-donating abilities of C(sp³)–H bonds of nitrogen-containing heterocycles in hydrogen atom transfer reaction

α‐Hydrogen spirocyclic alkoxyamines synthesis: ESR verified Nitroxides generation and their potential application in NMP polymerization

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Thermodynamic Evaluation on Alkoxyamines of TEMPO Derivatives, Stable Alkoxyamines or Potential Radical Donors?

Cited by 4 publications

References 111 publications

Organic Synthesis Using Nitroxides

Organic Synthesis Using Nitroxides

Quantitative evaluation of H-donating abilities of C(sp3)–H bonds of nitrogen-containing heterocycles in hydrogen atom transfer reaction

α‐Hydrogen spirocyclic alkoxyamines synthesis: ESR verified Nitroxides generation and their potential application in NMP polymerization

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Product

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Quantitative evaluation of H-donating abilities of C(sp³)–H bonds of nitrogen-containing heterocycles in hydrogen atom transfer reaction